Spindle motor, and disk drive apparatus including the spindle motor

ABSTRACT

A spindle motor includes a shaft arranged to extend in an axial direction, and a base portion arranged to define a portion of a housing, and including a through hole in which the shaft is inserted. A fixing region is defined between an inner circumferential portion of the base portion and a lower portion of the shaft. The fixing region includes a press-fitting region and an adhesion region defined on a lower side of the press-fitting region and in which a seal gap is defined between the inner circumferential portion of the base portion and the lower portion of the shaft. The seal gap is arranged to gradually decrease in radial width with increasing height. The seal gap is arranged to include an adhesive arranged therein over an entire circumference thereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spindle motor and more specificallyto a spindle motor for use in a disk drive apparatus.

2. Description of the Related Art

In recent years, in accordance with increased storage density of disks,there has been a demand for disk drive apparatuses, such as hard diskdrives, to control rotation of the disks, movement of heads, and so onwith high precision. In a known hard disk drive (HDD) disclosed in JP-A2006-40423, a gas arranged in an interior of the HDD is a low-densitygas, such as a helium gas or a hydrogen gas, and the HDD is therebyarranged to achieve a reduction in resistance of the gas against a disk,a head, and so on during rotation of a spindle motor. The reduction inthe resistance of the gas against the disk, the head, and so oncontributes to reducing vibration of the disk, the head, and so on,enabling highly precise data recording.

Bases of some spindle motors (hereinafter referred to simply as“motors”) installed in HDDs are defined by portions of housings of theHDDs. In the case where the interior of the HDD is filled with a gassuch as a helium gas or the like as described in JP-A 2006-40423, thehelium gas, for example, which has extremely small molecules, tends toeasily leak out of the interior of the HDD to an outside of the HDD.Therefore, in the case where a shaft is fixed in a through hole definedin the base, it is not easy to ensure sufficient sealing of a region inwhich the base and the shaft are fixed to each other.

SUMMARY OF THE INVENTION

A spindle motor according to a preferred embodiment of the presentinvention preferably is used in a disk drive apparatus including ahousing defining an interior space. The spindle motor includes astationary portion, a base portion, and a rotating portion. Thestationary portion preferably includes a shaft arranged to extend in anaxial direction. The base portion is preferably arranged to define aportion of the housing and includes a through hole in which the shaft isinserted. The rotating portion is arranged to rotate about a centralaxis with respect to the stationary portion.

The base portion preferably includes an inner circumferential portionarranged to define the through hole. The inner circumferential portionand a lower portion of the shaft define a fixing region therebetween.The fixing region preferably includes a press-fitting region and anadhesion region defined on a lower side of the press-fitting region. Inthe adhesion region, a seal gap is preferably defined between the innercircumferential portion of the base portion and the lower portion of theshaft.

The seal gap is preferably arranged to gradually decrease in radialwidth with increasing height. In addition, the seal gap is arranged toinclude an adhesive arranged therein over an entire circumferencethereof.

A spindle motor according to another preferred embodiment of the presentinvention is preferably used in a disk drive apparatus including ahousing defining an interior space. The spindle motor includes astationary portion, a base portion, and a rotating portion. Thestationary portion preferably includes a shaft arranged to extend in anaxial direction. The base portion is preferably arranged to define aportion of the housing and includes a through hole in which the shaft isinserted. The rotating portion is arranged to rotate about a centralaxis with respect to the stationary portion.

The base portion includes an inner circumferential portion arranged todefine the through hole. The inner circumferential portion and a lowerportion of the shaft define a fixing region therebetween. The fixingregion preferably includes a press-fitting region and an adhesion regiondefined on a lower side of the press-fitting region. In the adhesionregion, a seal gap is defined between the inner circumferential portionof the base portion and the lower portion of the shaft.

One of the lower portion of the shaft and a lower end portion of aninner circumferential surface of the inner circumferential portion ofthe base portion preferably includes a recessed portion arranged to bein connection with the seal gap. The seal gap and a space in the throughhole abutting on the recessed portion are preferably arranged to includean adhesive arranged continuously therein, with the adhesive beingarranged over an entire circumference of the seal gap.

A spindle motor according to yet another preferred embodiment of thepresent invention is preferably used in a disk drive apparatus includinga housing defining an interior space. The spindle motor includes astationary portion, a base portion, and a rotating portion. Thestationary portion preferably includes a shaft arranged to extend in anaxial direction. The base portion is preferably arranged to define aportion of the housing, and includes a through hole in which the shaftis inserted. The rotating portion is arranged to rotate about a centralaxis with respect to the stationary portion.

The base portion preferably includes an inner circumferential portionarranged to define the through hole. The inner circumferential portionand a lower portion of the shaft define a fixing region therebetween.The fixing region includes a press-fitting region and an adhesion regiondefined on a lower side of the press-fitting region. In the adhesionregion, a seal gap is preferably defined between the innercircumferential portion of the base portion and the lower portion of theshaft.

The seal gap is arranged to include an adhesive arranged therein over anentire circumference thereof. An increased-width gap portion ispreferably defined at a boundary between the seal gap and thepress-fitting region or in a portion of the seal gap which is in avicinity of the press-fitting region. The increased-width gap portionhas an increased radial width and extends over an entire circumference.

A communicating channel is defined within the base portion or betweenthe lower portion of the shaft and the inner circumferential portion ofthe base portion to connect the increased-width gap portion with a spacedefined on an upper side of an upper surface of the base portion.

A spindle motor according to yet another preferred embodiment of thepresent invention is preferably used in a disk drive apparatus includinga housing defining an interior space. The spindle motor includes astationary portion, a base portion, and a rotating portion. Thestationary portion preferably includes a shaft arranged to extend in anaxial direction. The base portion is preferably arranged to define aportion of the housing and includes a through hole in which the shaft isinserted. The rotating portion is arranged to rotate about a centralaxis with respect to the stationary portion through a bearing mechanism.

The shaft preferably includes a non-through hole portion, a firstconnection channel, and a second connection channel. The non-throughhole portion is arranged to extend downward from an upper end of theshaft. The first connection channel is arranged to extend from the holeportion in a radial direction to connect the hole portion with aninterior of the bearing mechanism. The second connection channel isarranged to extend from the hole portion in the radial direction toconnect the hole portion with a space defined on a lower side of thebearing mechanism.

Various preferred embodiments of the present invention are able toprevent a gas arranged in an interior of a housing from leaking out ofthe housing.

Also, various preferred embodiments of the present invention arearranged to achieve an improvement in perpendicularity of the upper endsurface of the thrust portion with respect to the outside surface of theshaft.

The above and other elements, features, steps, characteristics andadvantages of the present invention will become more apparent from thefollowing detailed description of the preferred embodiments withreference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a disk drive apparatus according to afirst preferred embodiment of the present invention.

FIG. 2 is a diagram illustrating a motor according to the firstpreferred embodiment of the present invention.

FIG. 3 is a diagram illustrating a bearing mechanism according to thefirst preferred embodiment of the present invention.

FIG. 4 is a diagram illustrating a lower portion of a shaft and itsvicinity according to the first preferred embodiment of the presentinvention.

FIG. 5 is a diagram illustrating the lower portion of the shaft and itsvicinity according to the first preferred embodiment of the presentinvention.

FIG. 6 is a flowchart illustrating a procedure of assembling the motoraccording to the first preferred embodiment of the present invention.

FIG. 7 is a diagram illustrating the lower portion of the shaft and itsvicinity according to the first preferred embodiment of the presentinvention.

FIG. 8 is a diagram illustrating a portion of a motor according to amodification of the first preferred embodiment of the present invention.

FIG. 9 is a flowchart illustrating a procedure of assembling the motoraccording to a modification of the first preferred embodiment of thepresent invention.

FIG. 10 is a diagram illustrating the motor in the course of assemblingthereof according to a modification of the first preferred embodiment ofthe present invention.

FIG. 11 is a diagram illustrating a lower portion of a shaft of a motorand its vicinity according to a second preferred embodiment of thepresent invention.

FIG. 12 is a bottom view of the shaft and a base plate according to thesecond preferred embodiment of the present invention.

FIG. 13 is a flowchart illustrating a procedure of assembling the motoraccording to the second preferred embodiment of the present invention.

FIG. 14 is a diagram illustrating a lower portion of a shaft of a motorand its vicinity according to a third preferred embodiment of thepresent invention.

FIG. 15 is a cross-sectional view of the shaft and a base plateaccording to the third preferred embodiment of the present invention.

FIG. 16 is a diagram illustrating a lower portion of a shaft of a motorand its vicinity according to a fourth preferred embodiment of thepresent invention.

FIG. 17 is a plan view of a base plate according to the fourth preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is assumed herein that a vertical direction is defined as a directionin which a central axis of a motor extends, and that an upper side and alower side along the central axis in FIG. 1 are referred to simply as anupper side and a lower side, respectively. It should be noted, however,that the above definitions of the vertical direction and the upper andlower sides should not be construed to restrict relative positions ordirections of different members or portions when the motor is actuallyinstalled in a device. Also note that a direction parallel orsubstantially parallel to the central axis is referred to by the term“axial direction”, “axial”, or “axially”, that radial directionscentered on the central axis are simply referred to by the term “radialdirection”, “radial”, or “radially”, and that a circumferentialdirection about the central axis is simply referred to by the term“circumferential direction”, “circumferential”, or “circumferentially”.

FIG. 1 is a vertical cross-sectional view of a disk drive apparatus 1including a spindle motor (hereinafter referred to simply as a “motor”)12 according to a first preferred embodiment of the present invention.The disk drive apparatus 1 is a so-called hard disk drive. The diskdrive apparatus 1 preferably includes, for example, three disc-shapeddisks 11, on which information is recorded, the motor 12, an accessportion 13, a clamper 151, and a housing 14. The motor 12 is arranged torotate while holding the disks 11. The access portion 13 is arranged toperform at least one of reading and writing of information from or tothe disks 11. Note that the number of disks 11 may be other than threeif so desired. Also note that the access portion 13 may be arranged toperform both the reading and the writing of information from or to thedisks 11.

The housing 14 preferably includes a first housing member 141 and asecond housing member 142, the second housing member 142 preferablyhaving the shape of a flat plate. The disks 11, the motor 12, the accessportion 13, and the clamper 151 are contained in the housing 14. Thefirst housing member 141 and the second housing member 142 arepreferably joined to each other through, for example, welding or by anyother suitable methods to define the housing 14 of the disk driveapparatus 1. An interior space 143 of the housing 14 is hermeticallyenclosed, and includes no or substantially no dirt or dust. The interiorspace 143 of the housing 14 is preferably filled with a low-density gas,such as, for example, helium gas.

The three disks 11 are preferably arranged at substantially regularintervals in an axial direction through spacers 152, and arranged to beclamped by the clamper 151 and the motor 12. The access portion 13preferably includes six heads 131, six arms 132, and a head actuatormechanism 133. Each of the arms 132 is arranged to support a separateone of the heads 131. Each of the heads 131 is arranged to magneticallyread and/or write information from or to a corresponding one of thedisks 11 while being arranged in close proximity to the disk 11. Thehead actuator mechanism 133 is arranged to actuate each of the arms 132to move an associated one of the heads 131 relative to a correspondingone of the disks 11. The head 131 is thereby arranged to access adesired location on the rotating disk 11 while being arranged in closeproximity to the disk 11, to carry out the reading and/or writing of theinformation.

FIG. 2 is a vertical cross-sectional view of the motor 12. The motor 12is preferably an outer-rotor motor. The motor 12 includes a stationaryportion 2, a rotating portion 3, and a fluid dynamic bearing mechanism4. The fluid dynamic bearing mechanism 4 will be hereinafter referred toas a “bearing mechanism 4”. The rotating portion 3 is supported throughthe bearing mechanism 4 to be rotatable about a central axis J1 of themotor 12 with respect to the stationary portion 2. The central axis J1of the motor 12 preferably coincides with a central axis of each of thestationary portion 2, the rotating portion 3, and the bearing mechanism4.

The stationary portion 2 preferably includes a base plate 21, which isan example of a base portion, a stator 22, and a wiring 24. The baseplate 21 is arranged to define a portion of the first housing member 141illustrated in FIG. 1. The base plate 21 includes a through hole 230extending in the axial direction therethrough defined in a centerthereof. The base plate 21 further includes one connector fitting hole162 defined therein at a position away from the through hole 230, asrepresented by a broken line in FIG. 1. The connector fitting hole 162is arranged to extend through the base plate 21. A connector 161 isarranged in the connector fitting hole 162. The connector fitting hole162 is preferably arranged to be sealed by the connector 161 and byanother method such as, for example, an application of an adhesive. Theconnector 161 is arranged to be connected to an external circuit 163outside the housing 14.

Referring to FIG. 2, the stator 22 is preferably fixed to the base plate21. The stator 22 includes a stator core 221 and coils 222 wound on thestator core 221. The wiring 24 is arranged to extend along an innerbottom surface 211 of the base plate 21. The inner bottom surface 211 isa surface that faces the interior space 143 of the housing 14illustrated in FIG. 1. The wiring 24 is arranged to extend from thestator 22 to the connector 161, which is represented by a broken line inFIG. 1. One end portion of the wiring 24 is connected to the connector161, while an opposite end portion thereof is connected to lead wires222 a leading from the coils 222 illustrated in FIG. 2. An example of apreferred form of the wiring 24 is a flexible printed circuit (FPC)board. However, the wiring 24 could also be defined by a wire or wirescontinuous with the lead wires 222 a.

The rotating portion 3 preferably includes a rotor hub 31 and a magneticmember 32. The rotor hub 31 includes a hub body 311, a cylindricalportion 312, and a disk mount portion 313. The cylindrical portion 312is arranged to project downward from an outer edge portion of the hubbody 311. The disk mount portion 313 is arranged to extend radiallyoutward from a bottom portion of the cylindrical portion 312. Themagnetic member 32 preferably includes a substantially cylindrical rotormagnet 321 and a back iron 322. The rotor magnet 321 is preferably fixedto an inside of the cylindrical portion 312 with the back iron 322 beingarranged therebetween. The rotor magnet 321 is arranged radiallyopposite the stator 22. A rotational torque is generated due to theinteraction between the magnetic flux generated by the stator 22 and therotor magnet 321.

The hub body 311 includes a central hole portion 311 a extending in theaxial direction and defined in a center thereof. A portion 5 of the hubbody 311 which is in the vicinity of the central axis J1 and whichincludes the central hole portion 311 a will be hereinafter referred toas a “sleeve portion 5”.

The bearing mechanism 4 preferably includes a shaft 41, a first coneportion 421, a second cone portion 422, a first cover member 431, asecond cover member 432, and a lubricating oil 49. The shaft 41 isinserted in the central hole portion 311 a of the sleeve portion 5. Alower portion 412 of the shaft is preferably fitted in the through hole230 of the base plate 21. The lower portion 412 refers to a portion ofthe shaft which is inserted in the through hole 230, and will behereinafter referred to as a “shaft lower portion 412”. A portion of thebase plate 21 which is in the vicinity of the central axis J1 and whichincludes the through hole 230 will be hereinafter referred to as an“inner circumferential portion 23”. The shaft 41 is arranged to extendin the vertical direction along the central axis J1. The shaft 41includes a non-through hole portion 411 defined in an interior thereof.The hole portion 411 is arranged to extend downward from an upper end ofthe shaft 41 along the central axis J1. The hole portion 411 is arrangedto have an axial length greater than the axial length of a non-throughregion 414. The non-through region 414 is defined on a lower side of thehole portion 411 and between the hole portion 411 and a small holeportion defined in a lower end portion of the shaft 41. An upper portionof the hole portion 411 includes a screw hole portion 410.

Referring to FIG. 1, a screw 153 is preferably inserted into the screwhole portion 410 and a hole portion 142 a defined in a center of thesecond housing member 142, which is arranged to cover an upper side ofthe motor 12. The second housing member 142 and the shaft 41 are therebyfixed to each other. A sealant 120 is preferably arranged at allcircumferential positions between an outer circumferential portion ofthe screw 153 and inner circumferential portions of both the screw holeportion 410 and the hole portion 142 a, and at all circumferentialpositions between an upper portion of the hole portion 142 a and a headportion 153 a of the screw 153. An example of the sealant 120 is anadhesive.

Referring to FIG. 2, the first cone portion 421 is fixed to the shaft 41on a lower side of the sleeve portion 5. An upper portion of an outsidesurface of the first cone portion 421 is arranged to be angled radiallyoutward with decreasing height, while a lower portion of the outsidesurface of the first cone portion 421 is preferably angled radiallyoutward with increasing height. The second cone portion 422 is fixed tothe shaft 41 on an upper side of the sleeve portion 5. As with the firstcone portion 421, an upper portion of an outside surface of the secondcone portion 422 is preferably angled radially outward with decreasingheight, while a lower portion of the outside surface of the second coneportion 422 is arranged to be angled radially outward with increasingheight.

FIG. 3 is a diagram illustrating the bearing mechanism 4 in an enlargedform. A lower portion of an inside surface 52 of the central holeportion 311 a of the sleeve portion 5 is arranged to be angled radiallyoutward with decreasing height, while an upper portion of the insidesurface 52 is arranged to be angled radially outward with increasingheight.

A first inclined gap 64, which is preferably angled radially outwardwith decreasing height, is defined between the lower portion of theinside surface 52 of the sleeve portion 5 and the upper portion of theoutside surface of the first cone portion 421. A second inclined gap 65,which is preferably angled radially outward with increasing height, isdefined between the upper portion of the inside surface 52 of the sleeveportion 5 and the lower portion of the outside surface of the secondcone portion 422.

The first cover member 431 is attached to a bottom portion of the sleeveportion 5, and is arranged opposite to the outside surface of the firstcone portion 421. The second cover member 432 is attached to a topportion of the sleeve portion 5, and is arranged to cover the outsidesurface and an upper end of the second cone portion 422.

The lubricating oil 49 is preferably arranged in two locations, namely,in the first inclined gap 64 and in the second inclined gap 65. Surfacesof the lubricating oil 49 arranged in the first inclined gap 64 arelocated in a gap 61 defined between the first cover member 431 and thefirst cone portion 421, and in a lower portion of a middle gap 63defined between the shaft 41 and a middle portion of the sleeve portion5. Surfaces of the lubricating oil 49 arranged in the second inclinedgap 65 are located in a gap 62 defined between the second cover member432 and the second cone portion 422, and in an upper portion of themiddle gap 63.

The shaft 41 preferably includes a first communicating portion 411 a anda second communicating portion 411 b defined therein. The firstcommunicating portion 411 a is preferably a first connection channelarranged to establish radial communication between the hole portion 411,which is defined in the interior of the shaft 41, and the middle gap 63,which is arranged in an interior of the bearing mechanism 4. The secondcommunicating portion 411 b is preferably a second connection channelarranged to establish radial communication between the hole portion 411and a space 25 defined on an upper side of an upper surface 212 of theinner circumferential portion 23, i.e., a space on a lower side of thebearing mechanism 4. An end opening of the second communicating portion411 b is arranged in the vicinity of the surface of the lubricating oil49 located in the gap 61 defined between the first cover member 431 andthe first cone portion 421. The middle gap 63 is arranged to be incommunication with the space 25 on the lower side of the bearingmechanism 4 through the first communicating portion 411 a, the holeportion 411, and the second communicating portion 411 b. Pressure in themiddle gap 63 is thereby arranged to be equal to or substantially equalto pressure in the interior space 143 of the disk drive apparatus 1. Asa result, balance between the upper and lower surfaces of thelubricating oil 49 held in the first inclined gap 64 is maintained in asubstantially constant state. Similarly, balance between the upper andlower surfaces of the lubricating oil 49 held in the second inclined gap65 is also maintained in a substantially constant state.

While the motor 12 is driven, a fluid dynamic pressure is generatedthrough the lubricating oil 49 in each of the first inclined gap 64 andthe second inclined gap 65. The sleeve portion 5 is thereby supported tobe rotatable with respect to the shaft 41. In the motor 12, the sleeveportion 5 is arranged to define a portion of the bearing mechanism 4 asa portion supported by the shaft 41. That is, the sleeve portion 5 is aportion of the rotating portion 3 and a portion of the bearing mechanism4 at the same time.

In the motor 12, the axial length of the hole portion 411 is greaterthan the axial length of the non-through region 414 makes it possible toarrange the second communicating portion 411 b in a lower portion of thebearing mechanism 4, and also to arrange the first cone portion 421 inthe lower portion of the bearing mechanism 4. As a result, bearingportions which are defined in the first inclined gap 64 and the secondinclined gap 65 and each of which is arranged to generate a fluiddynamic pressure in the lubricating oil 49 can be arranged at asufficient axial distance from each other to achieve an improvement inbearing rigidity of the bearing mechanism 4.

FIG. 4 is a diagram illustrating the shaft lower portion 412 of themotor 12 and its vicinity in an enlarged form. An outer circumferentialsurface 413 of the shaft lower portion 412, which is a portion of theshaft 41 which is inserted in the through hole 230, is a cylindricalsurface centered on the central axis J1. Hereinafter, the outercircumferential surface 413 will be referred to as an “inserted outercircumferential surface 413”. An upper portion 231 of an innercircumferential surface 23 a of the inner circumferential portion 23includes a cylindrical surface centered on the central axis J1.Hereinafter, the upper portion 231 will be referred to as an “innercircumferential surface upper portion 231”. A lower portion 232 of theinner circumferential surface 23 a includes an angled surface which isarranged to gradually decrease in diameter with increasing height.Hereinafter, the lower portion 232 will be referred to as an “innercircumferential surface lower portion 232”.

An upper portion of the inserted outer circumferential surface 413 ispress fitted in the inner circumferential surface upper portion 231.Hereinafter, a region defined between the upper portion of the insertedouter circumferential surface 413 and the inner circumferential surfaceupper portion 231 will be referred to as a “press-fitting region 81”.Regarding the shaft 41, a lower end 411 c of the hole portion 411, whichis defined in the interior of the shaft 41, is arranged at a levelslightly lower than that of an upper end of the press-fitting region 81.The hole portion 411 is thus arranged to overlap in a radial directionwith the press-fitting region 81. To be more accurate, an axialextension range 911 of the hole portion 411 and an axial extension range912 of the press-fitting region 81 are arranged to overlap with eachother. In the motor 12, the axial length of a range 913 over which thetwo axial extension ranges 911 and 912 overlap with each other ispreferably arranged to be about half or less than about half the axiallength of the press-fitting region 81, for example. As a result, in thepresent preferred embodiment, a sufficient strength of the press fit ofthe shaft 41 to the base plate 21 is achieved as opposed to the casewhere the entire press-fitting region 81 is arranged to overlap with theaxial extension range 912 of the hole portion.

A seal gap 821 is defined between a lower portion of the inserted outercircumferential surface 413 and the inner circumferential surface lowerportion 232. The seal gap 821 is arranged to gradually decrease inradial width with increasing height. An adhesive 7 is preferablyarranged in the seal gap 821 over an entire circumference thereof, sothat the shaft lower portion 412 is adhered to the inner circumferentialportion 23. The adhesive 7 is preferably an epoxy thermosettingadhesive. Hereinafter, a substantially cylindrical region in which theseal gap 821 is defined will be referred to as an “adhesion region 82”.Note that the adhesive 7 may be arranged in the press-fitting region 81as well. As described above, the shaft 41 is preferably fixed to theinner circumferential portion 23 through both press fit and adhesion.Hereinafter, an entire region including the press-fitting region 81,which is defined between the inner circumferential portion 23 and theshaft lower portion 412, and the adhesion region 82, which is defined ona lower side of the press-fitting region 81, will be referred to as a“fixing region 8”.

Referring to FIG. 5, the axial length 921 of the adhesion region 82 andthe axial length 922 of the press-fitting region 81 within the fixingregion 8 are preferably arranged to be equal or substantially equal toeach other. An angle θ defined between the inner circumferential surfacelower portion 232 and the inserted outer circumferential surface 413 ofthe shaft lower portion 412 in a cross-section of the innercircumferential portion 23 and the shaft 41 taken on a plane includingthe central axis J1, i.e., an angle of the seal gap 821, is preferablyarranged to be in the range of about 3 degrees to about 4 degrees.Referring to FIG. 4, on a lower side of the adhesion region 82, anannular chamfer portion 83 is preferably defined by a chamfer 831defined in a lower end portion of the inserted outer circumferentialsurface 413 and a chamfer 832 defined in a lower end portion of theinner circumferential surface 23 a. The annular chamfer portion 83 isarranged to gradually increase in radial width with decreasing height.

In the motor 12, the adhesive 7 is preferably arranged in the seal gap821 over the entire circumference thereof to seal a gap defined betweenthe shaft 41 and the inner circumferential portion 23. This contributesto preventing the gas arranged in the interior of the housing 14 fromleaking out through the gap defined between the shaft 41 and the innercircumferential portion 23.

FIG. 6 is a flowchart illustrating a procedure of assembling the motor12. First, the stationary portion 2 illustrated in FIG. 2 is assembled,and the rotating portion 3 and the bearing mechanism 4 are assembled asa single assembly 121 (steps S11 and S12). Note that the stationaryportion 2 may be assembled after or simultaneously with the assembly ofthe assembly 121. The same holds true for other preferred embodiments ofthe present invention described below.

Next, referring to FIG. 4, the shaft lower portion 412 is press fittedinto the through hole 230 of the inner circumferential portion 23 (stepS13). As a result, the shaft 41 is temporarily fixed to the base plate21 in the fixing region 8. Referring to FIG. 7, the assembly 121 and thestationary portion 2 are turned upside down, and the adhesive 7, whichis now in a liquid state, is applied preferably to a single location inthe annular chamfer portion 83 (step S14). The adhesive 7 then entersinto the seal gap 821, traveling downward in FIG. 7, i.e., in thedirection of the press-fitting region 81, and preferably spreads evenlyin a circumferential direction in the seal gap 821. At this time, airinside the seal gap 821 travels to an outside of the base plate 21through a portion of the annular chamfer portion 83 where the adhesive 7is not applied. That is, the air is replaced by the adhesive 7 as aresult of the spread of the adhesive 7 in the seal gap 821 and theaccompanying travel of the air inside the seal gap 821 to the outside ofthe base plate 21. A sufficient spreading of the adhesive 7 throughoutthe seal gap 821 is achieved by capillary action to thereby permitlittle or no air to remain in the seal gap 821. Air remaining in theseal gap results in a decrease in the area (including the axial length)of the adhesion region, which may lead to an increased likelihood of agas passing through the adhesion region. In the present preferredembodiment, the air is replaced by the adhesive 7 in the seal gap 821according to the above-described mechanism, to secure a sufficient areaof the adhesion region 82.

After the spreading of the adhesive 7 throughout the entire seal gap 821is complete, the stationary portion 2 and the assembly 121 are carriedinto a heating device, and the adhesive 7 is heated and cured (stepS15). As a result, the assembly 121 and the base plate 21 are securelyfixed to each other to complete an operation of assembling the motor 12.During the assembly of the motor 12, the shaft 41 is temporarily fixedto the base plate 21, and this eliminates a need to use a large-scalejig to fix relative positions of the stationary portion and the assemblyin the heating device as would be required if the shaft and the baseplate were to be fixed to each other through only the adhesive. This inturn facilitates the operation of assembling the motor 12.

The structure of the motor 12 and the operation of assembling the motor12 according to the first preferred embodiment have been describedabove. In the disk drive apparatus 1 including the motor 12, theadhesive 7 is arranged in the seal gap 821 over the entire circumferencethereof, and this contributes to preventing the internal gas fromleaking out through the gap defined between the shaft 41 and the innercircumferential portion 23. The technique of sealing the seal gap 821with the adhesive 7 is particularly suitable for a case where theinternal gas is a helium gas. Even if the base plate 21 of the diskdrive apparatus 1 needs to have a small thickness in order to enable alarge number of disks 11 to be mounted in the disk drive apparatus 1while reducing the height of the disk drive apparatus 1, adoption of theabove-described technique makes it possible to seal the gap definedbetween the shaft 41 and the base plate 21.

The seal gap 821 is arranged to have a so-called tapered shape,gradually decreasing in radial width with increasing height. Thiscontributes to causing the adhesive 7 to spread into the seal gap 821.This contributes to preventing air from remaining in the seal gap 821.As a result, an improvement in reliability of the disk drive apparatus 1is achieved.

The hole portion 411 defined in the interior of the shaft 41 does notextend through the shaft 41 in the axial direction. This contributes topreventing the internal gas from passing through the hole portion 411and leaking out downwardly of the base plate 21.

The sealant 120 is arranged at all circumferential positions between theupper portion of the hole portion 142 a of the second housing member 142and the head portion 153 a of the screw 153. This contributes topreventing the gas arranged inside the disk drive apparatus 1 fromleaking out through a slight gap defined between the second housingmember 142 and the head portion 153 a of the screw 153. Moreover, thesealant 120 is also arranged at all circumferential positions betweenthe outer circumferential portion of the screw 153 and the innercircumferential portions of both the screw hole portion 410 and the holeportion 142 a. This contributes to more securely preventing a leakage ofthe gas.

Referring to FIG. 8, in a motor 12 according to a modification of thefirst preferred embodiment, the axial extension range 911 of the holeportion 411 and the axial extension range 912 of the press-fittingregion 81 may be arranged not to overlap with each other. In this case,an increase in the strength of the press fit of the shaft 41 to the baseplate 21 is achieved.

The axial length 921 of the adhesion region 82 and the axial length 922of the press-fitting region 81 within the fixing region 8 are arrangedto be equal or substantially equal to each other. This enables asufficient amount of the adhesive to be arranged between the shaft 41and the inner circumferential portion 23 to achieve the sealing. Theaxial length of the adhesion region 82 is preferably arranged to be inthe range between about half the axial length of the press-fittingregion 81 and about twice the axial length of the press-fitting region81. The sealing of the gap defined between the shaft 41 and the baseplate 21 with the adhesive 7 is thereby achieved. The same holds truefor other preferred embodiments of the present invention describedbelow.

In the motor 12, the angle of the seal gap 821 is preferably arranged tobe in the range of about 3 degrees to about 4 degrees to retain theadhesive 7 therein, for example. A leakage of the gas arranged insidethe disk drive apparatus 1 can be thereby prevented. The angle of theseal gap 821 is preferably arranged to be more than about 0.1 degrees,for example, in order to allow a sufficient amount of the adhesive 7 tobe held in the seal gap 821. In addition, the angle of the seal gap 821is preferably arranged to be less than about 10 degrees, for example, inorder to securely prevent the internal gas from penetrating through theadhesive 7 and leaking out of the base plate 21. The angle of the sealgap 821 is more preferably arranged to be in the range of about 0.2degrees to about 4 degrees, and still more preferably arranged to be inthe range of about 3 degrees to about 4 degrees, for example.

Note that a hydrogen gas, instead of the helium gas, may also be used asthe gas fed into the interior of the housing 14 of the disk driveapparatus 1. Also note that a mixture of the helium gas and the hydrogengas may be used as the gas fed into the interior of the housing 14 ifdesired. Also note that a mixture of air and any one of the helium gas,the hydrogen gas, and the mixture of the helium gas and the hydrogen gasmay be used as the gas fed into the interior of the housing 14. The sameholds true for other preferred embodiments of the present inventiondescribed below.

The adhesive 7 used in the motor 12 is preferably a thermosettingadhesive, for example. In this case, the adhesive is able to fix theshaft 41 and the base plate 21 to each other with a greater jointstrength than in the case where the adhesive 7 possesses only ananaerobic property or only a UV-curing property. A variety of adhesivesthat possess the anaerobic property and/or the UV-curing property may beused in the motor 12, as long as the adhesives possess a thermosettingproperty. The same holds true for other preferred embodiments of thepresent invention described below.

Next, a procedure of assembling the motor 12 according to a modificationof the first preferred embodiment will now be described below withreference to FIG. 9. First, as in the above-described operation ofassembling the motor 12, the stationary portion 2 as illustrated in FIG.2 is assembled, and the rotating portion 3 and the bearing mechanism 4are assembled as the single assembly 121 (steps S21 and S22). Next,referring to FIG. 10, the adhesive 7, which is now in the liquid state,is applied to all circumferential positions on the inner circumferentialsurface upper portion 231 of the inner circumferential portion 23 (stepS23). The shaft 41 is inserted from above into the inner circumferentialportion 23, so that the shaft lower portion 412 is press fitted to theinner circumferential surface upper portion 231 (step S24).

At this time, the adhesive 7 is spread to the inner circumferentialsurface lower portion 232 in accordance with movement of the shaft 41.The adhesive 7 is held in the seal gap 821 over the entire circumferencethereof as illustrated FIG. 4. In the motor 12, the adhesive 7 alsoserves as a lubricant to facilitate the insertion of the shaft 41. Thebase plate 21 is thereafter heated, and the adhesive 7 is cured (stepS25) to complete the operation of assembling the motor 12.

In the motor 12, the adhesive 7 is arranged in the seal gap 821 over theentire circumference thereof. This contributes to preventing the gasarranged inside the disk drive apparatus 1 from leaking out through thegap defined between the shaft 41 and the inner circumferential portion23. The adhesive 7 is held in the entire seal gap 821 through capillaryaction, so that air is prevented from remaining in the seal gap 821.Note that in the assembly of the motor 12, the adhesive 7, which is thenin the liquid state, may be applied to both the inserted outercircumferential surface 413 of the shaft lower portion 412 and the innercircumferential surface upper portion 231.

FIG. 11 is a diagram illustrating a shaft lower portion 412 of a motoraccording to a second preferred embodiment of the present invention andits vicinity in an enlarged form. An inner circumferential portion 23 ofa base plate 21 preferably includes an inner circumferential surfaceupper portion 231 and a portion 233 defined on a lower side of the innercircumferential surface upper portion 231 and which is defined by acylindrical surface having a diameter slightly greater than that of theinner circumferential surface upper portion 231. Hereinafter, theportion 233 will be referred to as an “inner circumferential surfacelower portion 233”. In FIG. 11, the greater diameter of the innercircumferential surface lower portion 233 is emphasized. The same holdstrue for FIGS. 14 and 16 referenced below. FIG. 12 is a bottom view ofthe base plate 21 and the shaft lower portion 412. In FIG. 12, a lowersurface of the base plate 21 and an adhesive 7 are indicated by paralleloblique lines. As illustrated in FIGS. 11 and 12, a recessed portion 833which is recessed upward is defined in a portion of a lower end portion230 a of an inner circumferential surface 23 a of the innercircumferential portion 23. The lower end portion 230 a includes achamfer 832 defined therein except at the recessed portion 833.

In the motor according to the second preferred embodiment, the recessedportion 833, the chamfer 832, and a chamfer 831 defined in a lower endportion of an inserted outer circumferential surface 413 of the shaftlower portion 412 are arranged to together define an annular chamferportion 83 a which is recessed upward as with the annular chamferportion 83 a according to the first preferred embodiment. The motoraccording to the second preferred embodiment is otherwise preferablysimilar in structure to the motor 12 according to the first preferredembodiment. Accordingly, like members or portions are designated by likereference numerals, and redundant description is omitted.

Referring to FIG. 11, a seal gap 821 extending parallel or substantiallyparallel to a central axis J1 is defined in an adhesion region 82 adefined between the inner circumferential surface lower portion 233 andthe inserted outer circumferential surface 413. The seal gap 821 isarranged to be in connection with the recessed portion 833. The adhesive7 is arranged to extend continuously in the recessed portion 833 and theseal gap 821. In the seal gap 821, the adhesive 7 is arranged over anentire circumference thereof. As a result, a gap defined between a shaft41 and the inner circumferential portion 23 is sealed.

FIG. 13 is a flowchart illustrating a procedure of assembling the motoraccording to the second preferred embodiment. First, as with theprocedure according to the first preferred embodiment, a stationaryportion 2 is assembled, and a rotating portion 3 and a bearing mechanism4 are assembled as a single assembly 121 (steps S31 and S32). Next, theadhesive 7, which is now in the liquid state, is applied to allcircumferential positions on the inner circumferential surface upperportion 231 of the inner circumferential portion 23 in a manner similarto that illustrated in FIG. 10 (step S33). Referring to FIG. 11, theshaft lower portion 412 is press fitted to the inner circumferentialportion 23 (step S34). At this time, the adhesive 7 is spread to theinner circumferential surface lower portion 233. The seal gap 821 isdefined between the inserted outer circumferential surface 413 of theshaft lower portion 412 and the inner circumferential surface lowerportion 233, and most of the adhesive 7 is held in the seal gap 821.

Next, referring to FIG. 12, with the base plate 21 turned upside down,an additional adhesive 7, which is now in the liquid state, is appliedto the recessed portion 833 in the annular chamfer portion 83 a (stepS35). The adhesive 7 travels in the direction of the press-fittingregion 81 illustrated in FIG. 11 into the seal gap 821, that is, to thefar side of the page of FIG. 12, and the adhesive 7 is spreadsubstantially evenly in the circumferential direction. At this time, airinside the seal gap 821 travels through a portion of the annular chamferportion 83 which does not abut on the recessed portion 833 to an outsideof the base plate 21, so that little or no air remains in the seal gap821. The adhesive 7 is thereafter heated and cured (step S36) tocomplete the operation of assembling the motor.

Also in the motor according to the second preferred embodiment, theadhesive 7 is arranged in the seal gap 821 over the entire circumferencethereof, and this contributes to preventing the internal gas fromleaking out through the gap defined between the shaft 41 and the innercircumferential portion 23. Moreover, after the shaft 41 is temporarilyfixed to the base plate 21, the adhesive 7, which is then in the liquidstate, is applied to only the recessed portion 833 in the annularchamfer portion 83 a. This contributes to efficiently discharging theair inside the seal gap 821 to the outside of the base plate 21 througha portion of the annular chamfer portion 83 a which does not abut on therecessed portion 833. That is, the air inside the seal gap 821 is causedto travel to the outside of the base plate 21 in parallel with thespreading of the adhesive 7 through the seal gap 821, so that the air isreplaced by the adhesive 7.

FIG. 14 is a diagram illustrating a shaft lower portion 412 of a motoraccording to a third preferred embodiment of the present invention andits vicinity. As with the second preferred embodiment, an innercircumferential surface 23 b of an inner circumferential portion 23includes an inner circumferential surface upper portion 231 defined by acylindrical surface, and an inner circumferential surface lower portion233 defined by a cylindrical surface having a diameter slightly greaterthan that of the inner circumferential surface upper portion 231. Afirst groove portion 234 which is annular and which extends in thecircumferential direction is defined between the inner circumferentialsurface upper portion 231 and the inner circumferential surface lowerportion 233. At least one second groove portion 235, each of whichextends in the axial direction, is defined in the inner circumferentialsurface upper portion 231. That is, the inner circumferential portion 23according to the third preferred embodiment preferably is similar instructure to the inner circumferential portion 23 according to thesecond preferred embodiment except that the recessed portion 833 iseliminated, and that the first groove portion 234 and the second grooveportion(s) 235 are provided. The motor according to the third preferredembodiment preferably is similar in structure to the motor 12 accordingto the first preferred embodiment except in the structure of the innercircumferential portion 23. Accordingly, like members or portions aredesignated by like reference numerals, and redundant description isomitted. Note that the number of second groove portions 235 may be morethan one.

In a fixing region 8, a gap 841 extending over an entire circumferenceis defined between the first groove portion 234 and an inserted outercircumferential surface 413 of the shaft lower portion 412. The gap 841is defined at a boundary between a press-fitting region 81 and anadhesion region 82, that is, at a boundary between the seal gap 821 andthe press-fitting region 81. The gap 841 is arranged to be in connectionwith the seal gap 821. The radial width of the gap 841 is arranged to begreater than that of the seal gap 821. The gap 841 can be considered asa portion of the seal gap 821 which is arranged to have an increasedwidth. Hereinafter, the gap 841 will be referred to as an“increased-width gap portion 841”.

FIG. 15 is a cross-sectional view of a shaft 41 and a base plate 21illustrated in FIG. 14 taken along line A-A in FIG. 14. Referring toFIGS. 14 and 15, a communicating channel 842 extending in the axialdirection is defined between the second groove portion 235 and theinserted outer circumferential surface 413. The communicating channel842 is arranged to connect the increased-width gap portion 841 with aspace 25 defined on an upper side of an upper surface 212 of the innercircumferential portion 23 illustrated in FIG. 14. The radial width ofthe communicating channel 842 is preferably greater than that of theseal gap 821. The communicating channel may be defined either within abase portion or between a lower portion of the shaft 41 and an innercircumferential portion 23 of the base portion.

A procedure of assembling the motor according to the third preferredembodiment is preferably similar to that according to the secondpreferred embodiment. When the shaft lower portion 412 is inserted intothe inner circumferential portion 23, the shaft lower portion 412 ispress fitted to the inner circumferential portion 23 in a situation inwhich an adhesive 7, which is now in the liquid state, has been appliedto all circumferential positions on the inner circumferential surfaceupper portion 231. At this time, the adhesive 7 is caused to spread intothe increased-width gap portion 841. Note, however, that the amount ofthe adhesive 7 is adjusted so that the adhesive 7 may not fill up theincreased-width gap portion 841 and the communicating channel 842.

Next, with the base plate 21 turned upside down, an additional adhesive7, which is now in the liquid state, is preferably applied to allcircumferential positions in an annular chamfer portion 83. The adhesive7 travels in the direction of the increased-width gap portion 841 intothe seal gap 821. At this time, air inside the seal gap 821 travelsthrough the increased-width gap portion 841 and the communicatingchannel 842 to the space 25 defined on the upper side of the uppersurface 212 of the base plate 21.

The adhesive 7 is spread substantially evenly in the entire seal gap821. Thereafter, the base plate 21 is heated to cure the adhesive 7.

In the third preferred embodiment, as well as in the first preferredembodiment, the adhesive 7 is arranged in the seal gap 821 over theentire circumference thereof, and this contributes to preventing aleakage of a gas arranged inside a disk drive apparatus 1. Moreover, byproviding the increased-width gap portion 841 and the communicatingchannel 842, it is possible to more securely prevent air from remainingin the seal gap 821. Even if air remains in a portion of the seal gap821 which is in the vicinity of the increased-width gap portion 841, theair is caused to travel through the increased-width gap portion 841 andthe communicating channel 842 to the space 25 when the base plate 21 isheated, which prevents an increase in pressure in the seal gap 821 dueto an expansion of the air. This contributes to preventing the adhesive7 from leaking out of the seal gap 821.

In the third preferred embodiment, the adhesive 7 may be arranged in theincreased-width gap portion 841 over an entire circumference thereof.Also, the adhesive 7 may be arranged to close a lower portion of thecommunicating channel 842. Also, if the adhesive 7 applied in the firstinstance does not close the communicating channel 842 when the shaft 41is inserted into the inner circumferential portion 23, the radial widthof the communicating channel 842 may be arranged to be equal to that ofthe seal gap 821. In the assembly of the motor, the adhesive 7 may beapplied to the annular chamfer portion 83 in a situation in which alower surface of the base plate 21 is arranged to face downward. Even inthis case, the adhesive 7 is allowed to enter into the seal gap 821through capillary action. The same holds true for a fourth preferredembodiment of the present invention described below.

FIG. 16 is a diagram illustrating a shaft lower portion 412 of a motoraccording to the fourth preferred embodiment and its vicinity. FIG. 17is a plan view of an inner circumferential portion 23 of a base plate21. In FIG. 17, an upper surface 212 of the inner circumferentialportion 23 is indicated by parallel oblique lines. In place of thesecond groove portion 235 illustrated in FIGS. 14 and 15, a hole portion236 is defined in the inner circumferential portion 23. The hole portion236 is arranged near a through hole 230, and arranged to extend from theupper surface 212 in the axial direction. The motor according to thefourth preferred embodiment preferably is otherwise similar in structureto the motor according to the third preferred embodiment. A portion ofan increased-width gap portion 841 is arranged to be in connection witha radially inner portion of an inside surface of the hole portion 236.In the fourth preferred embodiment, the hole portion 236 preferablydefines a communicating channel that joins the increased-width gapportion 841 to a space 25 defined on an upper side of the innercircumferential portion 23.

A procedure of assembling the motor according to the fourth preferredembodiment preferably is similar to the procedure of assembling themotor according to the third preferred embodiment. In the assembly ofthe motor, an adhesive 7 applied to an annular chamfer portion 83illustrated in FIG. 16 enters into a seal gap 821, so that air insidethe seal gap 821 is caused to travel to the space 25 through theincreased-width gap portion 841 and the hole portion 236. Thiscontributes to securely preventing air from remaining in the seal gap821 as in the third preferred embodiment.

Also in the fourth preferred embodiment, the adhesive 7 is arranged inthe seal gap 821 over an entire circumference thereof, and thiscontributes to preventing a leakage of a gas arranged inside a diskdrive apparatus 1.

A method of manufacturing a spindle motor according to a preferredembodiment of the present invention preferably includes the steps of:press fitting a lower portion of a shaft into a through hole defined ina base portion; applying an adhesive to a seal gap which is defined on alower side of a press-fitting region between the lower portion of theshaft and an inner circumferential portion of the base portion, andwhich is arranged to gradually decrease in radial width with increasingheight; and curing the adhesive, which is arranged in the seal gap overan entire circumference thereof.

A method of manufacturing a spindle motor according to another preferredembodiment of the present invention preferably includes the steps of:applying an adhesive to an inner circumferential portion of a baseportion including a through hole defined therein; press fitting a lowerportion of a shaft into the through hole; and curing the adhesive, whichis arranged at all circumferential positions in a seal gap which isdefined on a lower side of a press-fitting region between the lowerportion of the shaft and the inner circumferential portion of the baseportion, and which is arranged to gradually decrease in radial widthwith increasing height.

A method of manufacturing a spindle motor according to yet anotherpreferred embodiment of the present invention preferably includes thesteps of: applying an adhesive to an inner circumferential portion of abase portion including a through hole defined therein; press fitting alower portion of a shaft into the through hole; applying an additionaladhesive to a recessed portion which is defined in the lower portion ofthe shaft or a lower end portion of an inner circumferential surface ofthe inner circumferential portion of the base portion, and which isarranged to be in connection with a seal gap defined on a lower side ofa press-fitting region between the lower portion of the shaft and theinner circumferential portion of the base portion; and curing theadhesive, which is arranged in the seal gap over an entire circumferencethereof.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises. While preferred embodiments of the present inventionhave been described above, it is to be understood that variations andmodifications will be apparent to those skilled in the art withoutdeparting from the scope and spirit of the present invention. The scopeof the present invention, therefore, is to be determined solely by thefollowing claims.

For example, in a modification of the first preferred embodiment, thelower portion of the inserted outer circumferential surface 413 may bedefined by an angled surface arranged to gradually decrease in diameterwith increasing height, and a seal gap may be defined between the lowerportion of the inserted outer circumferential surface 413 and the innercircumferential surface lower portion 232, which is defined by an angledsurface. In a modification of the second preferred embodiment, a portionof the chamfer 831 of the shaft lower portion 412 may include a recessedportion that is recessed upward in the annular chamfer portion 83 a.Also, both the shaft lower portion 412 and the inner circumferentialportion 23 may be arranged to include such recessed portions.

In the third preferred embodiment described above, the increased-widthgap portion 841 is preferably defined at the boundary between thepress-fitting region 81 and the seal gap 821. Note, however, that thisis not essential to the present invention. For example, in amodification of the third preferred embodiment, the increased-width gapportion may be defined, away from the aforementioned boundary in aportion of the seal gap 821 which is in the vicinity of thepress-fitting region 81. That is, it may be so arranged that a portionof the seal gap 821 is arranged below the aforementioned boundary, theincreased-width gap portion 841 is arranged below this portion of theseal gap 821, and the remaining portion of the seal gap 821 is arrangedbelow the increased-width gap portion 841. The same holds true for thefourth preferred embodiment.

Also, the inserted outer circumferential surface 413 of the shaft lowerportion 412 may be arranged to include an annular groove portion definedtherein as the increased-width gap portion 841. The inserted outercircumferential surface 413 may be arranged to include a groove portionextending in the axial direction and defined therein as thecommunicating channel 842. A plurality of communicating channels 842 maybe defined in the fixing region 8. In a modification of the fourthpreferred embodiment, a plurality of hole portions 236 may be provided.

In a modification of the first preferred embodiment, the annular chamferportion 83 may be provided with a recessed portion 833 as illustrated inFIG. 11. This contributes to more efficiently directing the adhesive 7into the seal gap 821. Also, an increased-width gap portion 841 and acommunicating channel 842 as illustrated in FIG. 14 may be definedbetween the shaft lower portion 412 and the inner circumferentialportion 23. In a modification of the first preferred embodiment, all ofthe recessed portion 833, the increased-width gap portion 841, and thecommunicating channel 842 may be provided. Furthermore, a hole portion236 as illustrated in FIG. 16 may be provided as a communicatingchannel. In a modification of the second preferred embodiment, anincreased-width gap portion 841 and a communicating channel 842 may bedefined between the shaft lower portion 412 and the innercircumferential portion 23. Also, a hole portion 236 may be provided asa communicating channel.

In a modification of each of the above-described preferred embodiments,the sealant may be arranged along all or only some of thecircumferential positions between the screw 153 and both the screw holeportion 410 of the shaft 41 and the hole portion 142 a of the secondhousing member 142, and/or along all circumferential positions betweenthe upper portion of the hole portion 142 a and the head portion 153 aof the screw 153. This contributes to prevention of a leakage of the gasarranged inside the disk drive apparatus 1. Also, the sealant may notnecessarily be an adhesive, but may be an annular resin memberpreferably made of rubber or the like, for example.

The adhesive 7 is applied to a portion of the annular chamfer portion 83at step S14 in FIG. 6 in the first preferred embodiment described above.Note, however, that the adhesive 7 may be applied to a plurality ofportions of the annular chamfer portion 83 or to all circumferentialpositions in the annular chamfer portion 83, as long as the air insidethe seal gap 821 can be properly discharged.

Features of the above-described preferred embodiments and themodifications thereof may be combined appropriately as long as noconflict arises.

Preferred embodiments of the present invention are applicable to spindlemotors for use in disk drive apparatuses, for example.

While preferred embodiments of the present invention have been describedabove, it is to be understood that variations and modifications will beapparent to those skilled in the art without departing from the scopeand spirit of the present invention. The scope of the present invention,therefore, is to be determined solely by the following claims.

What is claimed is:
 1. A spindle motor for use in a disk drive apparatusto drive a disk, the disk drive apparatus including a housing definingan interior space, the spindle motor comprising: a stationary portionincluding a shaft arranged to extend in an axial direction; a baseportion arranged to define a portion of the housing, and including athrough hole in which the shaft is inserted; and a rotating portionarranged to rotate about a central axis with respect to the stationaryportion; wherein the base portion includes an inner circumferentialportion arranged to define the through hole, the inner circumferentialportion and a lower portion of the shaft defining a fixing regiontherebetween; the fixing region includes a press-fitting region and anadhesion region defined on a lower side of the press-fitting region andin which a seal gap is defined between the inner circumferential portionof the base portion and the lower portion of the shaft; the seal gapincludes an adhesive arranged therein over an entire circumferencethereof; an increased-width gap portion is defined at a boundary betweenthe seal gap and the press-fitting region or in a portion of the sealgap which is in a vicinity of the press-fitting region, theincreased-width gap portion having an increased radial width andextending over an entire circumference; and a communicating channel isdefined within the base portion or between the lower portion of theshaft and the inner circumferential portion of the base portion toconnect the increased-width gap portion with a space defined on an upperside of an upper surface of the base portion.
 2. The spindle motoraccording to claim 1, wherein an inner circumferential surface of theinner circumferential portion of the base portion includes an innercircumferential surface upper portion and an inner circumferentialsurface lower portion; the base portion includes a first groove portiondefined between the inner circumferential surface upper portion and theinner circumferential surface lower portion, the first groove portionbeing annular and extending in a circumferential direction; and theincreased-width gap portion is defined between the first groove portionand an outer circumferential surface of the lower portion of the shaft.3. The spindle motor according to claim 1, wherein a radial width of thecommunicating channel is greater than a radial width of the seal gap. 4.The spindle motor according to claim 1, wherein an inner circumferentialsurface of the inner circumferential portion of the base portionincludes an inner circumferential surface upper portion and an innercircumferential surface lower portion; the base portion includes atleast one second groove portion defined in the inner circumferentialsurface upper portion, each second groove portion extending in the axialdirection; and the communicating channel is defined between each secondgroove portion and an outer circumferential surface of the lower portionof the shaft.
 5. The spindle motor according to claim 1, wherein thebase portion includes a hole portion arranged near the through hole, andarranged to extend from the upper surface of the base portion in theaxial direction; and a portion of the increased-width gap portion isarranged to be in connection with a radially inner portion of an insidesurface of the hole portion.
 6. The spindle motor according to claim 1,wherein an annular chamfer portion is defined on a lower side of theadhesion region; and the annular chamfer portion is arranged togradually increase in radial width with decreasing height.
 7. Thespindle motor according to claim 1, wherein an axial length of theadhesion region is substantially equal to an axial length of thepress-fitting region.
 8. The spindle motor according to claim 1, whereinan axial length of the adhesion region is in a range between about halfan axial length of the press-fitting region and about twice the axiallength of the press-fitting region.
 9. A disk drive apparatuscomprising: the spindle motor of claim 1 arranged to rotate a disk; anaccess portion arranged to perform at least one of reading and writingof information from or to the disk; a clamper arranged to clamp the diskto the spindle motor; and a housing arranged to contain the disk, thespindle motor, the access portion, and the clamper.
 10. The disk driveapparatus according to claim 9, wherein an interior space of the housingis filled with one of helium gas, hydrogen gas, a mixture of helium gasand hydrogen gas, and a mixture of air and any one of helium gas,hydrogen gas, and a mixture of helium gas and hydrogen gas.